The present invention relates to the extraction of organic substances such as tall oil and turpentine or the components thereof from coniferous woods.
The removal of organic material from coniferous woods, especially those woods used in pulping operations, is important not only because of the value of the extracts, but also because of the opportunity it offers for improving the quality of the products made from pulps free of these materials. Among the procedures which have been suggested for removing these materials, is extraction with low molecular weight hydrocarbons, such as butane, as taught in U.S. Pat. No. 1,762,785 to Arthur D. Little. According to that procedure, a liquefied, normally-gaseous extractant is contacted with a coniferous wood under moderate temperatures and pressures. Removal of the extract requires heating and distillation. The extracted organic materials can be adversely affected during separation into their component parts. Further degrees of purification can also be affected. For example, crude tall oil, as normally removed from coniferous woods, is composed principally of rosin acids and fatty acids and separation of the two components is economically desirable. In U.S. Pat. No. 2,388,412, there is disclosed a process for extracting fatty acids from tall oil by contacting it with a liquid, normally-gaseous hydrocarbon at elevated temperatures and pressures.
Typically, as presently conducted, the extraction and recovery of tall oil and turpentine require the use of conditions which can cause degradation of either the extracts or the extracted wood.